Vistumbler - Vistumbler is a wireless network scanner for Windows Vista and Windows 7. Features:
inSSIDer - inSSIDer Essential makes it easy to maintain small business WiFi.
NetSpot - NetSpot is a free app for wireless site surveys, Wi-Fi analysis, and troubleshooting
Waircut - Free network audit app
TamoGraph Site Survey - Wi-Fi site coverage survey and modelling application
Ekahau HeatMapper - The Free Wi-Fi Coverage Mapping Site Survey Tool